I think Hong Kong is the ideal holiday destination. So much to do, good food, beaches, mountains, museums, I could easily spend 2 weeks there. But 4 nights is a good start.

The flights are only a few hours apart, so not much in it. I'd pick whichever hardware you prefer (currently 350 vs 789). The flights' long enough thanks to all the diversions that you can get a full meal and sleep on either.